This disclosure relates generally to corrosion-inhibiting compositions used as deicers, anti-icers or pre-wetting agents. Additionally, the invention relates to deicing and anti-icing compositions such as brine solutions with corrosion inhibitors.
Liquid deicing chemicals such as aqueous solutions of sodium chloride, magnesium chloride, and calcium chloride are being increasingly used both as deicing and anti-icing liquids by themselves, and as pre-wetting agents for rock deicing salt. Highway maintenance organizations are increasingly requiring that chloride deicing and anti-icing liquids contain corrosion inhibitors. A common requirement is that deicing liquids be at least 70% less corrosive than pure sodium chloride as measured by a standard industry alternate immersion corrosion test. Identification of suitable corrosion inhibitors for liquid deicers has proven to be a challenge. Phosphates have been used as corrosion inhibitors for solid sodium chloride-based deicers, but they are not sufficiently soluble in concentrated chloride brines to provide a liquid formula that meets customer specifications. Suitable corrosion inhibitors must be low cost, soluble in concentrated brine, and be environmentally acceptable.
Recently, agricultural by-products such as molasses, distiller's solubles, and corn steep liquor have been used as corrosion inhibitors for liquid deicers and anti-icers. A drawback to these inhibitors is that relatively high concentrations must be used to obtain the corrosion inhibition required by customers. Since the agricultural additives themselves often have little ice melting capacity, the need to use high concentrations also has the effect of reducing the ice melting capacity of the deicing compound.
Major components of many of these agricultural additives are simple sugars (e.g. mono and disaccharides). For example, the major constituents of cane molasses are sucrose, glucose, and fructose. Thus, another current approach currently in use is to add sources of refined sugars (e.g. corn syrup) to deicing compounds as corrosion inhibitors. However, this has the same disadvantage of crude agricultural by-products—namely, high concentrations of the sugar are required to achieve the necessary corrosion inhibition. This is undesirable because it decreases the ice melting capacity of the deicer. In addition, high amounts of these refined sugars impart a high biological oxygen demand to the compound. It is therefore desirable to find corrosion inhibitors that are effective at low concentrations in order to minimize cost, environmental impact, and attenuation of the deicer's ice-melting capacity.